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CHEM1B > Week 8 Thermodynamics > Flashcards

Week 8 Thermodynamics Flashcards

1
Q

What are the 3 Laws of Thermodynamics

A
  1. Energy can not be created nor destroyed (ΔE** univ**=0) and can be converted from one form to another (ΔE=q+w)
  2. Work can be completed converted to heat NOT the other way around. Heat flows down temperature gradient until equilibrium is reached. (ΔS univ greater than 0)
  3. Entropy of a perfect crystal approaches 0 as temperature approaches 0 Kelvin (UNATTAINABILITY)
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2
Q

Spontaneity

A

A Spontaneous process is one the occurs without ongoing external intervnetion

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3
Q

What is the difference between thermodynamics and kinetics

A
  • Thermodynamics deals with spontaneity of reaction/process
  • Kinetics deal with rates, or how fast, of a reaction/process (activation energy)
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4
Q

If there are 3 particles total, how many total macrostates are there

A

4 Macrostates: 3 on left, 3 on right, 2 on left and 1 on right, 2 on right and 1 on left

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5
Q

Macrostates

Also, what is the probability of being in a particular macrostate

A

Averaged configurations of particles that give the same time invariant macroscopic paramters like P,T,V, n
Prob. macro= # of microstates in macrostate/total # of microstates

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6
Q

How do you determine which macrostate would be adopted?

A

The one with the highest macrostate proability aka the largest number of microstates

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7
Q

Entropy equation and explain each part (IN MICRO)

A

S=k x lnW
- S= entropy, k is Boltzmanns constant (1.381 x 10^-23 J/K), W= # of microstates

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8
Q
  1. When is the highest entropy
  2. What is entropy a measure of FUNDAMENTALLY
  3. What is entropy on the macroscale
  4. What is the result of having high probable macrostates
  5. What is the preference of macrostates
A
  1. Highest entropy when in the most probable macrostate
  2. Entropy is a measure of probability of being in a particular macrostate
  3. Entropy is a measure of disorder/energy dispersal on macroscale meaning more spread out particles have more microstates
  4. Makes existing in low probability macrostates impossible
  5. Preference to more dispersed particles
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9
Q

Reversible vs Irreversible processes

What is the different in probabilities for both

A

Irreversible- Spontaneous process where there is extremely LOW likelihood of process of final macrostate going back to initital macrostate (Final macrostate is more probable because there are more microstates)
Reversible- Processes where the forward and backward are just as likely (Ini. and Fin. macrostates are equally probable since there are the same # of microstates)

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10
Q
  1. What is the statement of the 2nd Law
  2. What is the result of entropy being a state function
  3. ΔSuniverse equation
A
  1. ΔS univ is ≥ 0- Entropy of universe increases when a process is spontaneous and remains constant at equilibrium
  2. ΔS= Final-Initial, ΔS=products-reactants
  3. ΔSUniverse=ΔS sys + ΔS surr
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11
Q
  1. When a process is reversible, what is the system
  2. Where have we seen the concept of dynamic equilbrium?
  3. When is it not at dynamic equilibrium?
A
  1. At equilbrium
  2. Phase diagrams- along the lines (fusion curve ie)
  3. When the process is irreversible/spontaneous such as increasing the temp to go from S to G
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12
Q

What is the ΔS system equation
(explain each part)

A

ΔSsys=q(rev)/T
S=Entropy (J/K)
q(rev)= Heat of a reversible reaction
T: Temp in Kelvin

Many heat comes in J/mol, might have to multiply by moles! (fusion ie)

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13
Q

What physical states have the largest entropies, why is this the case

A

S Gas&raquo_space; S Liquid > S solid
DUE TO DISORDERLINESS

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14
Q

What is ΔS universe at equilibrium (reversible reaction) (universe, sys and surr)

A
  1. ΔSuniv=0
  2. Δsys+surr=0
  3. Δsurr=-ΔSsys
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15
Q

What is ΔS universe for a spontaneous, irreversible reaction (universe, sys, surr)

A
  1. ΔS univ>0
  2. Δssys+surr >0
  3. Δsurr>-ΔSsys
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16
Q

Why does the freezing of water show Temperatures dependence of ΔS surr

A
  • Freezing water=decrease of entropy to system
  • At temps below 0 C and 1 atm, freezing is spontaneous (Surr>Sys)
  • At temps above 0 C and 1 atm, freezing is non-spontaneous ( Surr< Sys)
17
Q

When do solids and liquids coexist in relation to entropy

A

At freezing point: ΔS sys=0, ΔS surr= ΔS sys

18
Q
  1. What is the result of surroundings being infintely large
  2. What is the equation for ΔS surr
  3. What is the manitude of ΔS surr= ?
A
  1. Require infintely large amounts of heat to increase temperature
  2. ΔS surr= -(ΔHsys/T)
  3. Magnite of ΔS surr=magnitude of ΔH sys (heat of system)

CHEM1B (12 decks)

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